PROJECT SUMMARY The renal microvasculature is the convergence point for inflammatory disorders and hypoxic injury that cause endothelial dysregulation and deterioration of the underlying extracellular matrix (ECM). Together, these changes lead to progressive kidney dysfunction and ultimately failure. The regulatory role of the microvasculature in general?and in particular the microvasculature of the kidney?extends beyond its blood carrying capacity, with global implications to total-body homeostasis. Despite development of animal models of renal vascular dysfunction, which are important components of scientific research, translation of therapeutic tools and knowledge from animals to humans is limited by inconsistent linkages between transgenic models of disease and human vascular physiology. New scientific understanding of the renal vasculature microenvironment, its ECM composition, and the interdependency of endothelial cells within it provide information to develop ex vivo models of renal microvasculature. However, bioengineered systems oftentimes oversimplify the complex, interdependent nature of renal endothelial biology and the necessary cross-talk with pericytes and stroma within the microenvironment. Despite new advances in photolithography and additive manufacturing, the tiny length scales typically found within the in vivo microvasculature cannot be replicated and thus fail to adequately recapitulate the renal microenvironment ex vivo. To address this deficiency, our multidisciplinary team developed a bio-replicative renal microvasculature that mimics the scale, ECM make-up and fluid mechanics of the normal kidney. The foundation for the scientific investigation is this vascularized scaffolding system that is supported by our published data demonstrating patent and perfusable arterial and venous circulation (Caralt et al., Am J Transplant, 2015) with strict control of hydrodynamics (Uzarski, et al., Tissue Eng Part C Methods, 2015) that together result in a bio-replicative ?test rig?. This platform provides unique opportunities to manipulate the ECM microenvironment with new technologies that unlock cellular function. To enable such an investigation, we developed Targetable ECM Modifiers (TEMs), a new biomaterial delivery system based upon our preliminary and published data (Jiang, et al. Biomacromolecules, 2016) demonstrating ability to discriminately target and shuttle bioactive agents to specific ECM sub-components. Our hypothesis is that endothelial repair leading to vascular restoration can be controlled by delivering bioactive materials to the matrix with specificity to influence endothelial cells at ECM interfaces. Our investigation is supported by data showing a 7-fold enrichment of growth factors within ECM scaffolds accessed by TEMs, compared to soluble factors delivered free in solution, leading to maintenance of an ex vivo vascular endothelium for 28 days where none developed in its absence. This investigation is further enabled by a multidisciplinary team of collaborators in bioengineering, nanotechnology, peptide chemistry and nephrology to tailor the ex vivo renal vasculature with a panel of TEMs to develop testing platforms to study disease and therapies to repair renal vascular injury and reverse kidney disease.